Amplifier Power Help Needed - AVS Forum
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post #1 of 13 Old 11-14-2012, 08:22 AM - Thread Starter
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Hey guys,

I jumped on a very good deal on a used Anthem Statement A5 amplifier about two months ago because I was set on getting an Anthem AVM50v Pre/Pro. However, after budgeting my expenses I have come to the realization that it would be a little reckless of me to buy the 50v, even at a good used price. Because of this, I am going to sell off my A5 amplifier and stick with using just my Anthem MRX700 receiver for power. However, I have a question:

I have Paradigm Signature speakers (S8 and C5) and a pair of Paradigm Surround 3's. They are rated at 92dB (in-room). The MRX700 is rated at 90w per channel with 5 channels driven. My seating distance is 17ft away from the front three speakers (8ft away from the surround speakers).

Now, where I need help is determining how loud I am listening when I watch movies. The MRX700 calibrates "reference level" at 85dB (-20dBFS). When I watch a movie, the MV is typically at -15, sometimes -12. Does this mean that I am ultimately watching movies at 70-73dB (85-12), with peaks of 90-93dB?

I am trying to figure out what dB loudness to plug in when using an amplifier calculator, such as the one on Crown Audio's website. I just want to make sure I can continue watching movies at my usual volume without the A5 amplifier.


Thanks!
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post #2 of 13 Old 11-14-2012, 08:27 AM
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^^^

try it, maybe? you have the equipment there... smile.gif

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my build thread - updated 8-20-12 - new seating installed and projector isolation solution

 

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post #3 of 13 Old 11-14-2012, 08:48 AM - Thread Starter
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Yea, I plan on watching a few movies before sending the A5 away just to make darn sure.

But I also wanted to run the calculations (the nerd in me) to also double check.
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post #4 of 13 Old 11-14-2012, 08:55 AM
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^^^

lol, yea, i know that "nerd" part.... redface.gifbiggrin.gif

thing is, if you are crossing to a sub (which i'm assuming you are), those calculators can be (are) a bit skewed...

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my build thread - updated 8-20-12 - new seating installed and projector isolation solution

 

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post #5 of 13 Old 11-14-2012, 09:01 AM - Thread Starter
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Yea, I'm crossing to a Sub 25 @60 Hz (that's what ARC calculated was best crossover's for the front three).

I do not believe I have ever heard clipping from running out of amp power in any of my setups before. When I test out just using the MRX700, will it be completely noticeable if it cannot handle the power demand on it's own?
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post #6 of 13 Old 11-14-2012, 09:05 AM
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^^^

yea, it should be if you listen closely...

alternatively, it will go into protection...

one thing that "we" have found with audyssey (not sure how arc works)... the calculated xovers (even when using the pro kit) don't always provide the best mesh... again, not sure if that's true of arc or not, you'd have to measure... one of these days, i'd like to try out arc, many people seem to like it...

- chris

 

my build thread - updated 8-20-12 - new seating installed and projector isolation solution

 

http://www.avsforum.com/t/1332917/ccotenj-finally-gets-a-projector

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post #7 of 13 Old 11-14-2012, 11:14 AM - Thread Starter
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Is my assumption correct, though, that since the MRX700 calibrates to 85dB (-20dBFS, which means an overall maximum level of 105dB during brief peaks of the movie soundtrack), then me watching with the master volume at -12 means I am listening at 73dB (which means an overall maximum of 93dB during brief peaks in the soundtrack)?

Just want to make sure I have it correct in my head.
Thanks!
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post #8 of 13 Old 11-14-2012, 11:21 AM
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If it calibrates so 0 on the dial is 85 dB SPL at the listening position and you listen at -12 then that would be 73 dB SPL, yes, and you have an additional 12 dB of headroom over the calibration point.

If max peaks were 105 dB they are now 12 dB lower, again true, and you are using 15.85x less power (power in dB = 10 log (P2/P1), 10^(12/10) = 15.85).

All assuming the volume indicator is calibrated in dB.

HTH - Don

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #9 of 13 Old 11-14-2012, 11:25 AM
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^^^

yea, what he said... smile.gif

logarithms make my head hurt... redface.gif

- chris

 

my build thread - updated 8-20-12 - new seating installed and projector isolation solution

 

http://www.avsforum.com/t/1332917/ccotenj-finally-gets-a-projector

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post #10 of 13 Old 11-14-2012, 11:51 AM - Thread Starter
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Thanks guys!

Glad to see I finally understand calibrated reference coherently.
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post #11 of 13 Old 11-14-2012, 07:13 PM - Thread Starter
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Well, I watched my go to scene for listening loud: Super 8 train crash scene. With just the MRX700 powering my system, I was still able to have the MV at -15, which is the loudest I have ever had it (for this scene) even with my A5 amp. Any louder is just ear shattering (literally....it's such a LOUD scene, not just bass but screeching metal and carnage all over).

Think it's safe to say I am OK to sell my A5 now?
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post #12 of 13 Old 11-14-2012, 08:02 PM
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An avr may be clipping but not be noticeable all the time. A monentary clipping during a loud movie passage may go un-notice, or the dynamic of the scene will be blunted. Also, with loud music the amp can only produce a power max output before the wave is cut. In this case the bass and trebble may be at the same voulume and the instument separation is compromised. Worse case, the speaker or amp is damaged. This is usually proceeded by audible distortion.

Klipsch RF 7 based HT 7.4, Pioneer SC 35, Acurus Five 200 amp, Chase SS 18.2(2), VS 18.1(2), Samsung BDP F 7500, Asus/My Book Live HPC 4 TB

Yaquin VK 2100 amp, McIntosh XR 5 speakers, Samsung BDP F 7500
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post #13 of 13 Old 11-14-2012, 09:40 PM
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With efficient speakers, you don't need a whole lot of power.

i'm sure your 90watts is plenty for reference level with 92db speakers.

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